The present invention relates to wrist rest assemblies for use along the front edges of devices to be operated by a person""s hands or fingers, such as in front of a computer keyboard, computer mouse or other input device.
Wrist rest assemblies are known for use along the front edge of a device to be operated by a person""s hands or fingers, such as in front of a computer key board, computer mouse or other input device. It has been suggested that the use of such wrist rest assemblies can restrict damage to wrists from prolonged use of such devices. Heretofore, however, known wrist rest assemblies have been formed with layers of cushioning material that do not provide the quality of support for the wrists that may be desired.
The present invention provides a wrist rest assembly for use along the front edge of a device to be operated by a person""s hands or fingers, such as in front of a computer key board, computer mouse or other input device, which wrist rest assembly provides a layer of cushioning material that can provide better support for the wrists than has heretofore been provided, and further affords a degree of movement of the supported wrist relative to the surface on which the wrist rest is supported that has not been provided by known prior art wrist rest assemblies.
According to the present invention there is provided a wrist rest assembly comprising (1) a base having an upper pad support surface, which base has a bottom or supported surface adapted to be supported on a horizontal surface along the front edge of the device; and (2) a pad comprising a layer of gel. A bottom surface of the elongate pad is supported on the upper pad support surface of the base, and the pad has a sufficient width between its edges and thickness between its top and bottom surfaces (e.g., a thickness in the range of about xe2x85x9 inch to 5 inches and a width in the range of about xc2xd to 10 inches with the larger widths providing both wrist and fore arm support) to afford supporting a users wrists on the top surface to help keep the wrists in a neutral position with a portion of the layer of gel beneath and conforming to the supported wrists to distribute the weight of the wrists over a wide area and affording significant motion of the top surface of the pad with the supported wrists relative to the bottom surface in a plane generally parallel to the upper surface of the base.
Preferably the gel is a stable elastomeric block polymer gel similar to the gel described in U.S. Pat. No. 3,676,387, where the gels are polymer-oil combinations. The polymers are the A-B-A configurations wherein each block A is a glassy or resinous non-elastomeric thermoplastic polymer block with a glass transition temperature above room temperature, i.e., 25xc2x0 C., having an average molecular weight of between about 2,000 and 100,000 and which is relatively incompatible with the elastomeric polymer block B. B is an elastomeric block polymer of a conjugated diene, the average molecular weight between about 15,000 and 1,000,000 (preferably 15,000 to 250,000) and having a glass transition temperature considerably between that of blocks A. This difference in glass transition temperature may be as small as 15xc2x0 C., but is preferably at least 100xc2x0 C. and more preferably at least about 125xc2x0 C. The end blocks A of the block copolymer should constitute approximately 10 to 50 percent of the total polymer weight. Such block polymers and a method for their formation, are described in the U.S. Pat. No. 3,265,765 (Holden et al.) issued Aug. 9, 1966, and in general, these are quite suitable in the practice of the present invention.
Elastomeric First block copolymers of the type useful in the practice of this invention have been combined with oils to make oil extended rubbers and adhesives. In the formation of adhesives, the amount of oil is generally greater than in oil extended rubbers. The formation of adhesive compositions containing such block polymer tackifying resin and oil is described in U.S. Pat. No. 3,239,478 (Harlan, Jr.) issued Mar. 8, 1966. However, in none of the rubbers or adhesives just described does the amount of oil (compatible plasticizing oil) used constitute ordinarily even as much as 67 percent of the total composition, in as much as extension beyond this point will result in an adhesive with little or no cohesive strength. Further the oils recommended in Harlan are at least partially aromatic and such aromaticity results in a soft flowable material where large percentages of oil are used for the plasticizing effect. The use of a compatible oil is nonacceptable for purposes of the nonacceptable invention.
When an elastomeric block copolymer of the kind noted herein is combined with a non-aromatic paraffinic oil of low volatility with a flash point about 350xc2x0 F. and below about 500xc2x0 F., wherein the oil constitutes at least about 70 percent of the total weight of the block polymer-oil elastoplastic mixture, an extremely highly elastic material is obtained which is not only useful as such but which is capable of being melted upon heating for casting in the formation of molded or other articles at room temperatures. Stable elastomeric materials can be formed where the oil constitutes as much as 95 percent of the combined weight of the oil and elastomeric block copolymer. When the amount of the oil is less than about 70 percent the melt viscosity becomes excessive for convenient casting from a hot melt system. When the amount of oil is greater than about 95 percent, a thixotropic liquid results.
Paraffinic oils, which are normally considered incompatible with block polymers or other rubbers, and thus, not considered extender oils, are somewhat compatible with block copolymers at elevated temperatures (i.e., about 300xc2x0 F.) to the extent that the oil and the block copolymer form a mixture which when cooled, exhibits a novel structure which is neither gel nor extended polymer, but is rather a continuous web of one-dimensional polymer strands intermingled with a continuous phase of non-compatible oil. Microscopic examination of the oil polymer mixture reveals a sponge-like construction having voids therein filled with oil. The oil may be removed by mechanical means such as pressing, filtering, etc.
The oil used must be incompatible (non-solvent) with the non-elastomeric, thermoplastic polymer block A, should be of low volatility and should have a boiling point in excess of the melting temperature of the polymer-oil combination. For this purpose, ordinary paraffin-based petroleum oils such as mineral oil, petrolatum and other paraffin liquid petroleum products within the viscosity range of products commonly called oils are suitable in the practice of this invention. Unsuitable for purposes of the present invention are aromatic, naphthenic and cyclic containing oils.
Preferably, the gel is the gel described in Example No. II of British Patent No. GB 1,268,431 (which states xe2x80x9cA mixture of 5 parts xe2x80x9cNujolxe2x80x9d (Registered Trade Mark) brand U.S.P. mineral oil and one part styrene-isoprene-styrene block copolymer (xe2x80x9cKraton 107xe2x80x9d) was heated to approximately 149xc2x0 C. and agitated vigorously until the polymer appeared visually dissolved. Empty pint bottles were dipped into this hot sol so that a layer approximately 1.59 mm thick was desposited on the bottom rim. These bottles could be filled with water and dropped repeatedly onto concrete floor or steel plates without breakage.xe2x80x9d) except that the ratio of oil to block copolymer is in the range of 4 to 1 to 10 to 1 rather than being 5 to 1 as is described in that Example No. II. That gel is quite similar to the gel in the pad commercially available from Minnesota Mining and Manufacturing Company, St. Paul, Minn., under the trade designation xe2x80x9cRESTON (T.M.) Flotation Padxe2x80x9d, which pad for many years has been used in beds, wheel chairs and the like to prevent pressure points. Also, preferably the gel has a covering comprising an elongate tubular layer of flexible polymeric material (e.g., polyurethane) around the gel, which tubular layer has sealed ends to retain the gel and provides a flexible barrier to the escape of mineral oil from within the gel. The pad assembly can further include an outer layer over the top surface of the pad of a soft conformable material adapted for comfortable contact with a users wrists.
Preferably the base comprises a top portion having the upper pad support surface supporting the bottom surface of the elongate pad; a bottom portion having the bottom supported surface adapted to be supported on a horizontal surface; and means for supporting the top portion on the bottom portion with the elongate pad at a predetermined one of several different distances above the supported surface. That means is provided by the top portion of the base comprising longitudinally extending rails projecting outwardly in opposite directions generally parallel to its upper pad support surface, and the bottom portion including generally parallel spaced vertically upwardly projecting support portions having opposed surfaces defining sets of grooves parallel to the supported surface and vertically spaced along the support portions, each of which sets of grooves is adapted to receive the rails to support the top portion with the top surface of the elongate pad at a different distance above thy supported surface depending on which set of grooves the rails are engaged in.
While there might be advantages for some applications in allowing the top portion to reciprocate along the grooves of the bottom portion, thereby affording large transverse movements of the wrists with the top portion without relocating the wrists along the top surface of the pad; as illustrated the assembly includes means for releasably fixing the top portion relative to the bottom portions with corresponding ends of the top and bottom portions generally in alignment.
While the wrist rest assembly including its base is very useful, the base is not a necessity to using the pad. Thus generally the method according to the present invention for supporting the wrists of a person operating a device such as a computer keyboard, computer mouse or other input device comprises: (1) providing a pad comprising a layer of gel, which pad has opposite top and bottom surfaces, and opposite longitudinally extending edges; (2) supporting the pad along the front edge of the device; and (3) supporting the users wrists along the top surface of pad; the pad having a sufficient thickness between the top and bottom surfaces and width between the edges to have a portion of the layer of gel beneath and conforming to the supported wrists and to afford significant motion of the top surface of the pad with the supported wrists relative to the bottom surface in a horizontal plane.